Geol.— Vol. II.] ANDERSON— CRETACEOUS DEPOSITS. 



33 



Summary of Facts Appearing in the Lists. 



An examination of the preceding tabulated lists makes it 

 apparent that there are two distinct horizons in the Chico 

 of California and Oregon, each having a fauna to a consid- 

 erable extent peculiar to itself. A summary of the facts to 

 be gathered from this list is presented. It will be observed 

 also that the species belonging to the two divisions are 

 supplementary rather than similar. In the Lower Chico 

 there is shown a large number of cephalopods, several of 

 which are common to both the northern and southern 

 localities; only two of them, however, are certainly com- 

 mon to the upper and lower divisions. Similar facts will 

 be noticed for the other classes. Also, as will be seen 

 later, very few of the Chico forms are those of the Horse- 

 town portion of West Coast Cretaceous. Some of the 

 forms more characteristic for criteria of correlation are 

 those of the following lists: — 



Characteristic Forms of the Chico. 

 Lower Chico Forms. Upper Chico Forms. 



Acanthoceras sp. 

 Desmoceras hoffnianni 

 Desnioceras sugatum 

 Desmoceras ashlandicurn 



Baculites chico'ensis 

 Ancyloceras lineatum 

 Helicoceras breweri 

 Helicoceras declive 



